New Rugulosins, Anti-MRSA Antibiotics, Produced by Penicillium radicum FKI-3765-2

New rugulosins B (2) and C (3) were isolated together with known rugulosin (renamed rugulosin A in this paper, 1) from whole culture of Penicillium radicum FKI-3765-2, and their structures were elucidated by NMR spectroscopy. Rugulosins A and C were a homodimer of the same anthraquinone moieties, whereas rugulosin B was a heterodimer of analogous anthraquinone moieties. Rugulosins A to C showed antimicrobial activity against methicillin-resistant Staphylococcus aureus.